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H L Vader

Publications and source records attributed to H L Vader.

At least 37 records · Page 2Linked to original sources
PubMed1991

Androstanediolglucuronide: a parameter for peripheral androgen activity before and during therapy with cyproterone acetate.

Serum 5 alpha-androstane-3 alpha,17 beta-diolglucuronide (3 alpha-AdiolG) levels were measured and the degree of hirsutism was scored in female outpatients complaining of excessive hair growth before and during treatment with cyproterone acetate. In a group of 16 patients with idiopathic hirsutism and in a group of 9 patients with either polycystic ovary syndrome and hirsutism or 21-hydroxylase deficiency and hirsutism, the serum 3 alpha-AdiolG levels were significantly increased (p less than 0.01) as compared with the serum 3 alpha-AdiolG level in a control group of 13 apparently healthy women: 3 alpha-AdiolG levels, median (range), being 5.3 (2.3-7.8) nmol/l, 8.5 (4.1-10.4) nmol/l, and 2.9 (1.5-5.2) nmol/l, respectively. In contrast to a previous report, no correlation was found between the serum 3 alpha-AdiolG levels and the Quetelet Index (N = 18, R = 0.42, p greater than 0.05), indicating an apparent ineffectiveness of the excessive androgen turnover in fat tissue. The use of the anti-androgen drug cyproterone acetate alone or in combination with ethinylestradiol in reverse sequential therapy did lower the 3 alpha-AdiolG levels significantly (p less than 0.01) together with a significant decrease (p less than 0.01) in hirsutism score. From the results of this study we therefore conclude that 3 alpha-AdiolG can be used as a parameter for peripheral androgen action before and during treatment with anti-androgens.

Androgen Antagonists↗
PubMed1991

One-step chromogenic equivalent of activated partial thromboplastin time evaluated for clinical application.

We evaluated the clinical usefulness of a recently developed semi-automated one-step chromogenic equivalent of activated partial thromboplastin time (APTT; Behring). This simple test is easily adaptable for automation. Generally, the results with this chromogenic one-step APTT were at least as precise as those obtained with comparative coagulometric methods. The chromogenic one-step APTT showed, both in vitro and in vivo, adequate sensitivity to congenital intrinsic factor deficiency but no sensitivity to Factor VII deficiency. Unlike a two-step coagulometric APTT (Dade), the one-step chromogenic APTT seemed sensitive to activation products of the contact system, which are present in immunoadsorbed factor-deficient plasma. The in vitro sensitivity of the chromogenic APTT to heparin was comparable with that of a coagulometric APTT, but the sensitivity to heparin in patients' samples differed slightly. The chromogenic APTT is relatively insensitive to anomalies in the fibrinogen-fibrin conversion. Finally, we observed discrepancies between the chromogenic and coagulometric APTT results for plasma of patients with disseminated intravascular coagulation. We conclude that this one-step chromogenic APTT warrants further evaluation for possible use as a routine test for the clinical laboratory.

Amino Acid Sequence↗
PubMed1991

The spot test is not a reliable screening procedure for mucopolysaccharidoses.

To check the reliability of the Ames MPS paper spot test, which is based on the Azure A dye, we sent a series of urine samples to three laboratories where the spot test is part of the metabolic screening for mucopolysaccharidoses. In these laboratories false-negative results ranged between 19% and 35% and false-positive results ranged between 12% and 29% of all samples submitted. In contrast, the quantitative dimethylmethylene blue test (Clin Chem 1989;35:1472-7) detected an increased glycosaminoglycan content in all urine samples from mucopolysaccharidosis patients and gave no false-positive results. In the latter procedure, glycosaminoglycan content is expressed per millimole of creatinine, and age-dependent reference values are used. We conclude that the Ames spot test and other spot tests are unreliable as a screening procedure for mucopolysaccharidoses and should not be used to screen for these diseases.

Azure Stains↗
PubMed1990

Molar absorptivities of bilirubin (NIST SRM 916a) and its neutral and alkaline azopigments.

Three laboratories in the U.S. and two in the Netherlands determined molar absorptivities (epsilon) of Standard Reference Material (SRM) 916a Bilirubin from the National Institute of Standards and Technology. In caffeine reagent the average epsilon values were 50,060 and 48, 980 L.mol-1.cm-1 at 432 and 457 nm, respectively. The epsilon value of the blue azopigment, obtained with the Reference Method for total serum bilirubin, was 76,490 L.mol-1.cm-1 at 598 nm. When the addition of alkaline tartrate was omitted, the molar absorptivity of the red azopigment was 56,600 L.mol-1.cm-1 at 530 nm.

Azo Compounds↗
PubMed1988

Analysis of the aqueous phase of human cervical mucus by reversed-phase high-performance liquid chromatography and capillary isotachophoresis.

The aqueous phase of human cervical mucus was analysed by reversed-phase high-performance liquid chromatography (HPLC) and capillary isotachophoresis (ITP). With HPLC, seventeen ultraviolet-absorbing and eight fluorescent components and with ITP five anionic and four cationic components could be determined. The sample pre-treatment consisted of a simple ultrafiltration. Ten samples from fertile women and eleven samples from infertile women were analysed. In six samples from the infertile group higher median concentrations of several components were found. This may be an indication of disturbances in the biochemical processes of the cervical mucus of woman with fertility problems.

Cervix Mucus↗
PubMed1988

[Non-invasive method of arterial oxygen saturation monitoring in the neonatal intensive care unit (with a review of blood oxygen monitoring methods)].

Recently a new method (pulse oximetry) became available, which enables us to monitor non-invasively the arterial oxygen saturation in neonates. We tested this new method in several premature infants, from the time that oxygen therapy was instituted (IPPV; CPAP), in order to evaluate its potential clinical use. In stable patients we found a better correlation (r = 0.90) between the oxygen saturation measured transcutaneously and that measured in an arterial blood sample that the correlation (r = 0.22) between oxygen tensions measured either transcutaneously or in a blood sample. Although transcutaneous monitoring of the arterial oxygen saturation, especially because it is a continuous process, can be a valuable adjunct in monitoring premature infants who receive extra oxygen, it can not replace the necessity for intermittent blood sampling to determine 'arterial blood gases'. One should also remember that; due to the fact that the position of oxyhemoglobin dissociation curve depends on several factors; the SO2 can not simply be derived from the pO2 or vice versa. Continuous transcutaneous monitoring of oxygen saturation may decrease the frequency with which arterial blood samples for blood gas measurement have to be taken.

Blood Gas Analysis↗
PubMed1983

Influence of erythrocytes on direct potentiometric determination of sodium and potassium.

We have shown that the sodium concentration in whole blood measured by direct potentiometry is higher than in plasma. The 'erythrocyte-effect', already described by Siggaard Andersen, is most pronounced for instruments equipped with a reference electrode with an open static liquid junction and is thus a general phenomenon. Instruments with a modified liquid junction show less interference. The same phenomenon appears for the determination of the potassium concentration, although the difference between whole blood and plasma, when measured with instruments equipped with a modified liquid junction, can be neglected in practice.

Erythrocytes↗
PubMed1981

On the standardisation of the direct spectrophotometric bilirubin determination. Influence of the albumin source and the molar bilirubin: albumin ratio.

The influence of different albumin solutions and of the molar bilirubin/albumin ratio on the bilirubin concentration determined by the method for Hertz et al. was studied. There is good agreement between the true-bilirubin concentrations and those obtained by the Hertz method for bilirubin-HSA and bilirubin-serum solutions. Moreover the observed concentration is scarcely influenced by the molar ratio. Bilirubin standards in HSA-solutions can thus be used to standardise this method. Errors are introduced by preparing standards in BSA-solutions as the absorption spectrum of bilirubin-BSA is different from that of bilirubin-HSA.

Bilirubin↗
PubMed1978

On standardizing the determination of the plasma renin activity.

Basically, the determination of the plasma renin activity (PRA) consists of the in vitro generation of angiotensin I and the radioimmunological determination of angiotensin I. Since both steps can be performed in several ways, the results from different laboratories can hardly be compared. In this paper we have described the results of our attempts to standardize both steps of the PRA determination currently in use in our laboratory, against Research Standard A for Angiotensin I and the International Reference Preparation of Human Renin, both obtained from the Medical Research Council.

Angiotensin I↗
PubMed1977

Influence of ions on the antigen-antibody complex formation as measured by radioimmunoassay.

In this study, using radioimmunoassay techniques, we found that ions at concentrations in the order of 0.1 molar influence the antigen-antibody complex formation. The angiotensin I/anti-angiotensin I reaction was studied in detail. Particularly bivalent cations and anions with a strong chaotropic effect (SCN-, I- and ClO4-) were found to influence strongly the specific immunological reaction. However, NO3- had also a remarkably strong influence. We found that the equilibrium constant, rather than the number of binding sites of the antibody, is influenced by the ions. It should be borne in mind that relatively high concentrations of electrolyte (as compared with the concentrations of antigen and antibody) show this effect. Consequently, this effect is of less practical importance for routine radioimmunoassay than is, for example, the effect of pH. However, this phenomenon shows that the radioimmunoassay technique might be valuable not only for quantization of very low hormone concentrations in biological fluids, but has also important potential applications in physical and protein chemistry. Particularly, the high sensitivity of this technique and the possibility of studying a homogeneous reaction system might give it advantages over other techniques.

Animals↗
PubMed1977

Influence of the pH on the antigen-antibody coupling in angiotensin I radioimmunoassay. Its consequences for the determination of the plasma renin activity.

The antigen-antibody complex formation in the angiotensin I radioimmunoassay appears to be influenced by the pH of the radioimmunoassay incubation mixture. This may lead to erroneous results in the determination of the plasma renin activity, when an aliquot of a plasma sample, buffered at pH 6 for optimum renin activity is brought into a radioimmunoassay mixture of another pH, while the radioimmunoassay standards are not corrected for this pH shift. In our experiments we studied this general pH effect, and evaluated the effect on the New England Nuclear Angiotensin I radioimmunoassay procedure. We propose a slight modification of this radioimmunoassay kit.

Angiotensin II↗
PubMed1975

The influence of viscosity on dilution methods. Its problems in the determination of serum sodium.

Dilution with a roller-pump is a well known procedure in clinical chemistry. This method may be influenced by viscosity. A higher viscosity of the sample yields a lower sample output and consequently a larger dilution. If the substance to be determined in the diluted sample can be measured accurately, the influence of viscosity may be analysed easily. This was performed for serum sodium. It was shown that with extreme pathological viscosities (as are found e.g. in multiple myeloma and Waldenström's macroglobinemia) underestimations of more than 15% may occur. Especially for serum sodium, the physiological range of which is fairly small, this may provoke serious diagnostic and therapeutic problems. We propose to use viscosity independent dilution systems.

Blood Proteins↗
PubMed1975

The uptake and elimination of halothane in dogs: A two or multicompartment system? II: Evaluation of wash-in and wash-out curves.

In 14 mongrel dogs wash-in and wash-out curves for halothane were obtained from measurements of arterial blood, mixed venous blood and end-tidal gas. From a certain point in the wash-in period the halothane concentration of arterial blood can be calculated from the halothane concentration in end-tidal gas and the blood-gas partition coefficient for halothane. Analysis of the curves shows that they are composed of two exponential components suggesting the presence of two body compartments. The question of a two-compartment system versus a multi-compartment system in discussed.

Animals↗